How to Detect Displays on a Mac with OS X El Capitan, Yosemite, Mavericks

Typically when an external display is connected to a Mac, it will automatically be detected and start working instantly, with the Mac either extending the desktop or mirroring the screen over to the newly attached display output. Sometimes that doesn’t happen however, and when a secondary screen is not detected automatically by the Mac, you’ll want to trigger the “Detect Display” function in OS X.
Like some other features in new versions of OS X, the “Detect Displays” button is now hidden by default, no longer immediately visible in the Display Preferences of OS X El Capitan, OS X Yosemite, and OS X Mavericks. This does not indicate a problem with the Mac or with the external screen you wish to use, you simply have to toggle the Option key to make the detect feature visible and then be able to run the detection as usual. This applies to secondary displays of all types, whether it’s an external monitor, AirPlay mirroring, AirDisplay, a projector, an HDMI connection to a TV, or whatever other additional screen you have attempted to connect to the Mac. If you’re having any issues either showing the feature or getting an external screen to show up properly, this is what you’ll want to do.

Use Detect Displays for External Screens on a Mac in OS X

With the secondary display to detect already connected to the Mac, do the following:

Go to the  Apple menu and choose System Preferences

Choose the “Displays” panel

Hold down the “Option” key to show the “Detect Displays” button – note that it replaces the ‘Gather Windows’ button

Click on “Detect Displays” while holding down Option to use the function as intended

At this point the external screen should be found and work as usual, launching the secondary “Displays” window for that screen. Of course you’ll want to be sure the physical connection is secured for the external display, and if you’re having any issues check the cables to the LCD monitor, projector, or TV.

It should be pointed out that having the “Detect Displays” button not being visible in OS X Mavericks is not an indicator of a problem or a bug, and it’s certainly not indicative of an issue with the output device, it’s simply hidden from casual use, presumably because most of the time the Mac usually has no issues finding and connecting to external screens. Nonetheless, sometimes you have to forcibly detect an external display, which is why this feature is a little curious to hide by default.

Using the “detect” feature should be the first troubleshooting step taken if you can’t find a video output device that is connected to a Mac, though more advanced methods may need to be taken if there are other issues, such as flickering or noisy displays, which may require an SMC reset to resolve.

Enjoy this tip? Subscribe to the OSXDaily newsletter to get more of our great Apple tips, tricks, and important news delivered to your inbox! Enter your email address below:

If the above set of instructions don’t work, scroll all the way to the bottom of this thread to ‘Gerry-the-Merry’ comment. He explains the assistance he got from Mac. It worked for me. Beware, there are things that may get cleared out, for example the one I know about is clearing the wifi setup. I needed to reconnect to my wifi and needed my password.

I’ve had to do this a few times since I move back and forth from the office. I found that the instructions above could be more clear, so here we go:

1. Switch off Mac
2. Disconnect HDMI
3. Reconnect HDMI
4. While HOLDING Option key the whole time
– switch on Mac AND press Command+F1
5. You should see a screen with a picture of a hard drive and a dropdown asking for you to choose your WIFI. If you do not see this, you should start the process over
6. Select your router and enter your WIFI password

I’m a PC user trying to help my wife get her new iMAC to recognize an external monitor. It worked “plug-n-play” when first connected. Now the next day, no luck. So now you have to hold a keyboard key to make a feature visible that was always visible before? Found the “detect displays” button, but still doesn’t work. Do the software developers just want to torture us? Tell me again why Apple is superior to PCs.

Ditto, connecting to Denon receiver then to Sony projector. Everything worked great until I installed El Capitan. Now most times (though curiously not all) when I turn the Denon & Sony off and then back on, the Mac no longer knows anything about the home theater system. The only audio output listed is internal speakers or Airplay. Clicking Detect Display does nothing. I’m having to reboot my Mac Pro every day now. It’s a major pain. I can tell everything is fine on the Mac, aside form its HDMI sync, because I can use Screen Sharing to connect to it and display its current state. But I have to either use Screen Sharing and reboot from the Apple menu or ssh in and reboot from the command line to have the Mac see the Denon/Sony display. If anyone has any hints about fixing or working around this they would be much appreciated.

This works 100% the same in OS X El Capitan and OS X Yosemite, hold Option and the button will change to Detect Displays. Using Yosemite and El Capitan right now with external screens, use this frequently.

Odd that the detect display is hidden. Why would Mac do this? Why? That is the question. Steve Jobs would not approve. His point was to make things easy. This reminds me of the days of cntrl alt delete on PCs! Possibly computer scientists have finally gone off the deep end of the digital world since Jobs is not there now to slap them back into reality.

I agree completely – Apple is moving in the WRONG direction. In an effort to make things “Cleaner” looking they are making once easy tasks way more difficult. This is one of the best examples. Why on earth would you remove the “Detect Display” button? The space is still there, nothing else changed, they just removed the button. My guess is this is a direct result of Ive taking over Forstall’s responsibilities after Jobs death and somebody needs to rein him in and make him stick to hardware where he is best with clean minimalist looks!

Same problem here. Using a Dell P2310H that worked flawlessly until this morning when I put Al Capitan or whatever its called on it. Now it may as well be a dead monitor. Pretty frustrated about this, I need this landscape monitor for Eclipse – coding on a Macbook Pro even if the screen is pretty big is still a bit cramped.

This “fix” obviously doesn’t work for lots of people, including me on my brand new mac book pro. Occasionally I can make the 2nd monitor work by unplugging cable from monitor at the mac and plugging it into the other thunderbolt port. (Using Apple’s VGA to Thunderbolt converter). Otherwise, 5 to 10 minutes later, the second monitor wakes up. Talk about speedy processors…

Has anyone figured this out yet? I updated to El Capitan and can’t get the displays working. Option key will allow me to see the detect displays but nothing after that?
I need this to work for my class! Everything was all easy before upgrading!

Hi there
Still trying to connect my second screen which was working fine up until Christmas. The ‘detect display’ button appears but nothing happens. Have restarted, updated etc. but still doesn’t work. Incredibly frustrating.
Thanks for your help so far!

Same here. No worky. SMC reset, regular restart, nothing. I did that ridiculous Option trick for Detect Displays, and nothing. It was working last week and I’ve had El Capitan for ages. This sucks so much. Yosemite and El Capitan are the first OS’s since I started in 1999 to be full of bugs. My $200 Bose SoundLink mini is a paperweight now too. Super.
I am not wondering of Steve Jobs really did have that much influence on things. The next OS’s after he died have been the crappy ones. Many bugs.

Also have a Dell Monitor U2413 which I am trying to use as a second display … to no avail.

Been in touch with Apple twice. I was advised that a Thunderbolt cable would work. I bought one at the Apple store. The only port the cable fits into at the Dell is called, DPin. The Dell doesn’t recognize the hook up.

I was also advised to use a HDMI connection but that I would have to get a connector. I bought the recommended HDMI connector at the Apple store (Belkin).

The connector will accept the HDMI insert but the other ends of both the connector and the HDMI cable don’t fit either the iMac or the Dell.

I did the option thing in the Display screen. nothing happened. I repeated it for every device port on the Dell with nothing happening … also used the ‘scan sources’ feature on the Dell with the result being the same.

Hi Everyone – I have solved this problem with the help of telephone support. Initially I was disheartened after reading all that has been written in this particular article comments section, but luckily I managed to crack this.

I had earlier used a samsung with the mac mini, and straight out of the box, it matched with the samsung. It appears that this leaves the mac mini with the memory of the samsung. Hence when connecting with HDMI to a Sony Bravia, the mac mini did not recognise the Sony and vice versa.

I switched off the mac mini, disconnected the HDMI, connected it back, switched on the mac mini, AND HELD DOWN THE OPTION BUTTON THROUGHOUT, then pressed CMD+F1. That did the trick partially. Then i restarted the mac mini, as before. Everything now sings.

I also have a USB out to my DAC for music, which is the principal purpose of the mac mini. That has stayed undisturbed. But in the quicktime / ELMedia player etc. to play the movies in different formats, it is necessary to switch the output from built in speakers to an amplifier (painfully, every time) and then the sound comes from the amp-speaker combo and the picture from the TV.

The less elegant way to do all this is to have a Apple TV connected by ethernet or wifi to your router, and a mac mini to the same router, and then the Sony TV will accept anything your mac mini has, provided it is iTunes compatible.

If the apple TV is jailbriken, then you can use some other formats and a whole lot of other programs. There is plenty of literature around the how and why of apple Tv jailbreaking.

I had the same issue with my Macbook Pro and LG display. At work I connect with a VGA adapter to a very old display and at home I connect using HDMI to my LG. I guess something needs to be cleared in order to let the mac connect to a second device.

Anyway, I had to run through the procedure above twice, but it worked. Warning tho, it cleared my wifi connection and I had to dig around for that password I had on an index card. ;) So, if doing the above procedure, be aware that other things may get cleared out. I have no idea yet what else may have been cleared, we will see.